Glass installation is typically a three-stage process. First, a clear silane primer is applied to the glass or a ceramic frit deposited on the glass to clean and prepare the surface for bonding. Second, a primer, which is essentially a carbon black dispersion which also contains a compound having silane and/or isocyanate functionality, often referred to as “black-out primer”, is then applied over the top of the clear primer. Third, an adhesive is applied to the primed glass which is then installed into the structure. See, U.S. Pat. No. 5,370,905, incorporated herein by reference. The black-out primer can mar surfaces of a structure or vehicle on to which the black-out primer may be dripped during installation. U.S. Pat. No. 5,363,944 discloses a single-step primer system. The primer comprises an aqueous primer solution containing a silane coupling agent which is used to facilitate adhesion of a polymer to a non-porous inorganic substrate such as metal or glass. The silane coupling agent has an amino or a mercapto functional group which is capable of reacting with functional groups of the polymer and also has one or more hydrolyzable groups which react with the free-hydroxyl groups on the surface of the substrate. This system requires long dry times before an adhesive can be applied. For many commercial operations, such long dry times are unacceptable. This is especially true in automotive assembly plants wherein each operation needs to be completed in a short period of time.
Yao et al., U.S. Pat. No. 6,511,752 discloses the method for adhering a polyurethane based adhesive to a substrate which comprises applying an aqueous primer solution onto the substrate which comprises water, an amino titanate compound, and preferably, an epoxy silane having at least one epoxy group and at least two alkoxy groups. Thereafter, a polyurethane adhesive is applied to the primer treated surface. A reaction product is formed of the primer and polyurethane.
In order for a primer and adhesive system to be commercially viable, that system must provide a durable bond. “Durable bond” means that the adhesive holds the window into the structure for a period of years. As the structure to which window glass or plastic coated with an abrasion resistant coating is traditionally bonded lasts for a significant number of years, it is expected that the bond holding the glass or coated plastic into a structure also lasts a significant number of years. Hsieh et al., United States Patent Publication 2005/0126683 discloses a primer system comprising a) one or more organotitanates having four ligands wherein the ligands are hydrocarbyl, optionally containing one or more functional groups having one or more heteroatoms selected from the group comprising oxygen, nitrogen, phosphorus and sulfur wherein two or more of the ligands may form a cyclic structure; b) one or more mercaptosilanes; c) one or more polyaminosilanes; d) one or more secondary aminosilanes; and e) a solvent which dissolves the components of the composition. The system provides durable adhesion to the substrate, dries rapidly allowing for application of the adhesive to the treated surface, in a short of period of time after the application of a clear primer, and work well on a variety of frits. One problem with this system is that the adhesive does not bond to the surface of the substrate rapidly when exposed to cold temperatures. Despite the success of this invention there are frit systems, such as zinc based frit systems, which are difficult for some primer systems to facilitate bonding thereto. Primer systems can have difficulty bonding to float glass systems. A float glass system locates the frit between two sheets of glass and thus the primer/adhesive system is required to bond directly to a glass surface.
What is needed is a system which bonds glass or coated plastic into a structure which does not require black-out primer, which provides durable adhesion, does not require long dry times between application of the primer and application of the adhesive, bonds to a variety of ceramic frits and float glass facilitates rapid bonding of an adhesive to a substrate when exposed to cold conditions.